1. Field of the Invention
This invention relates to an apparatus for manufacturing screened cables, and particularly to an apparatus for manufacturing screened or shielded cables wherein even if a thin conductive tape having a wavy pattern (including corrugation, embossment, and any other suitable wavy pattern, but hereinafter referred to simply as "corrugated tape") is utilized for a layer as screening or shielding the cable or as an outer conductor for a coaxial cable, a cable core provided with an insulating layer can be longitidinally covered with such corrugated thin tape without deforming the corrugation thereof.
2. Description of the Prior Art
There has been proposed such screened cable, for example as shown in FIG. 1, wherein the circumference of a paper tape 2 wound around a cable core 1 is covered longitudinally with a corrugated aluminum tape 3, and then the resulting member has applied thereover a sheath 4.
In this type of screened cable, a corrugated aluminum tape 3 having a thickness of, for instance, 0.2 mm or more is used to withstand the pulling tension (e.g., the cable core 1 has a 15 mm outer diameter, and the aluminum tape 3 has a 1 mm wave crest and a 2.5 mm pitch) in order to avoid deformation of the member 3, even though the pulling tension of the cable is increased at the time of manufacturing the same.
FIG. 2 is an explanatory view showing an apparatus for manufacturing the above screened cable which comprises a delivery drum 5 around which the cable core 1 is wound, a taping machine 6 for winding the paper tape 2 around the cable core 1, a drum 7 for winding the corrugated aluminum tape 3 utilized for longitudinally covering the cable core 1 around which the paper tape 2 is wound, a forming die 8 for covering the cable core 1 provided with the paper tape 2 with the corrugated aluminum tape 3, a sheath extruder 9 for providing the sheath 4 around the outside of the longitudinally covered cable core, a cooler 10 for cooling the extruded sheath 4, and a wind-up drum 11 for pulling the resulting screened cable which has been cooled by means of the cooler 10 (a pulling capstan and like are omitted).
In the above apparatus, the paper tape 2 is wound around the cable core 1, transferred in the pulling direction thereof, by means of the taping machine 6. Then the resulting cable core is longitudinally covered with the corrugated aluminum tape 3, which has previously been wound around the aluminum tape drum 7, by means of the forming die 8 (for instance, the aluminum tape 3 has an overlapped dimension of 5 mm). Furthermore, the sheath 4 is provided around the longitudinally covered cable core to cover the same by means of the sheath extruder 9, and thereafter the resulting screened cable is cooled by the cooler 10. The screened cable thus manufactured is finally wound up by means of the wind-up drum 11.
However, in such conventional apparatus for manufacturing screened cables as mentioned above pulling tension applied to the corrugated aluminum tape 3 can not be relieved at the time of manufacturing the screened cables. Accordingly, there is such disadvantage that the corrugated aluminum tape 3 is deformed, thereby destroying the corrugation, if the pulling tension increases in response to speeding up of the manufacturing rate.
Particularly, since such a thin corrugated aluminum tape having a thickness of less than 0.2 mm is used in a small diameter screened cable, there is such disadvantage that it is difficult to manufacture such small diameter screened cables while maintaining a prescribed productivity.